Method of and means for connecting telephone apparatus.



. I .E. A. GRAY. METHOD OF AND MEANS FOR GONNEOTING TELEPHONE APPARATUS.

. APPLICATION FILED JULY 30, 1907. 1,002,388. Patented Sept. 5,1911.

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E.A.GRAY.

METHOD OF AND MEANS FOR OONNEGTING TELEPHONE APPARATUS.

APPLICATION FILED JULY 30, 1907.

1,002,388, Patented Sept. 5,1911.

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E. A. GRAY. METHOD OF AND, MEANS FOR CONNECTING TELEPHONE APPARATUS.

APPLIOATION FILED JULY 80, 1907. E 1 002 3 Patented Sept. 5, 1911.

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METHOD OF AND MEANS FOR CONNECTING TELEPHONE APPARATUS. APPLICATION I'ILIZD JULY 30, 1907.

1,002,388, Patented Sept. 5,1911.

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E. A. GRAY. METHOD OF AND MEANS FOR CONNECTING TELEPHONE APPARATUS.

APPLICATION FILED JULY 30, 1907.

Patented Sept. 5,1911.

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7 so that the total number of such appearances i installed in a ten-thousand-line exchange,

' and State of Massachusetts, have invented instance. Assume that the largest selecting ,UNiTEnLsTAr s PATENTOFFICEQYH ERNEST A. clear, 015 BOSTON, MASSACHUSETTS, ASSIGNOR 'ro AMERICAN TELEPHONE 2;.

AND TELEGRAPH YORK.

METHOD OF AND MEANS FOR CONNECTTNG TELEPHONE APPARATUS.

1,002,388, Specification of Letters Patent. Patented Sept, Application filed July so, 190?. seri riqo. 386,249. i To' all whom it may concern: .7 a Be it known that I, EnNEsr A. GRAY, rer mary selectors, which would pick out the Siding at Boston, in thecounty of Suffolk then an idle trunk-leading thereto. As each primary selector must have access to each group, its five hundred sets ofterminals must be divided into twenty sections, and, assigning the same number of trunks to each section, this would give twenty-five certain Improvements inilylethods of and Means for Connecting Telephone Apparatus, of which the following is a specification.

In telephone systems, in furnishing con; necting paths between a plurality of rimary points and other or secondary points, it is customary to so employ the intermediate trunks or conductors that each primary point has access to every trunk, or that separate and uniform groups of primary points are similarly. multipled to independent groups of trun'ks equal inwnumber. For example, if there. be ten trunks connecting'a. manual switchboard of twenty sections with, a private branch exchange, each ofHthe trunks will appear,-that is, will be represented by a switch terminal at each section,

hundred subscribers must often be expected Therefore, it becomes necessary to segrevisions that if satisfactory service is to be given the probability of more than twentythe same time will be slight. A typical -case of call distribution in an exchange of will equal two hrtndred or, referring to ai like group of ten trunks for uniting succeed ing points in an automatic switching system, if one hundred primary electromechanismsa are to make use of the trunks they must be, multipled thereto one thousand times. But in such an automatic or electromechanica'L switching system, it is often found that any class-of switches must be separated into divisions with independent groups Ofmultipled trunks, on account of'the. limitations of available commercial machines. The, latter case is one in which the present invention may be used with great advantage and {an application ofcmy improved method to a generally 'similar varrangement will hereinafter. be more particularly described. Therefore, the arrangement'of this divided multiple will be made clearer by a specific use in illustrating existing conditionsand finexplaining my invention.

Let it be assumed that-the average length iof, telephone conversations is two minutes, .-and that sufficient trunks must be provided to handle without delay all the calls of'the -.busiest two-minute period." Considering five hundred lines, suppose that traffic studies of such an tion show: that for it fifty seven calls may be expected during said busiest period, these falling by chance as regards theirfdistribuchines permitted, fifty-seven .trunks 1i uleach terminating in a connector would meet switch thatycan be efficiently empl0yed{has. the demands. But since, as previouslyjndifive hundred sets of fixed terminals, to each of which sets artrunk or subscribers line may be connected, and that they are to be but twenty-fiveterminals for each five-hunvisions.; .Of course the nnmberpf divisions The; wanted z'line will be finally, reached through some one.of twenty groups of secondaryr' selectors of five hundred lines each.

period, -Assr1me twelveof these designated We will herespeci ficallyconsider the pritrunks by means of which all of the ten. thousand subscribers could be connectedwith a called subscriber in a particular five-hum dred group. But, obviously, many more than twenty-five simultaneous calls for iivefive calls coming into any one division at jnowany one of the twenty final groups of dated, the primary selectorsfobtainable have 95 dred group,,they mustibeiseparated into die COMPANY, OF BOSTCN, MASSACHUSETTS, A CORPORATION OF NEW -proper one of these five-hundred groups and a vgate crthe-.prin1ary selectors into such di :this character will now be presented, for

exchangeas that in ques i tion through this period and also among the i primary points through which they are to, come. It-will be evident that ,if the matipled through all the primary selectors and must be such thatno. one will rcceivgni'ore than twenty-five calls during the busiest by the letters a to Z, inclusive, through which the fifty-seven calls are fortuitously dis tributed as tabulated below:

ot' the more busy trunks.

Divisions a b c d e f g h ijkl call ..-.-i-.-- 6 1 4. 7-810 6 5 a 0 5, 2

From this it app'ears that three isthe minimum number ofdivisions fromwhich twenty-five (-allshwould originate. Consequently twenty-five trunks can only be depended upon to care forany three divisions, through which they will be multipl ed, and since there are altogether four groups of three divisions each, a total of-one hundred trunks would be necessary. For two reasons the eificiency of a trunking system thus divided low. First, there is an excess of trunks for carrying the maximum load, since evidently those joined to the last terminal in the sections of twenty-five, say

the twentieth to. the twenty-fifth, with which the movable switching members last cooperate, will be seldom usedin any one groupan'd never in two simultaneously, yet they appear "in every division. Second, thereiis a needlessly frequent multipling the fact that those, over the terminals of \vhich'the movable contact arms first sweep. would invariably be used duringbusy periods of inultipled through only a portionof the'selectors of a group, are, never= theless, connectedto all.

, The purpose of thisjinvention is. to so connect primary orltransmitting points (by which is meant any apparatus in a. series througlravhich a-telephone call progresses, other-than that to be ultimately reached) and any apparatus later in the series (which may be termed secondary or desired oints) that the intermediate trunks or con actors will be highly eflicient. A condition is at least apprmiched in which the minimum number of trunks will provide without delay' for the calls of the busiestperiod and with a symmetrical distribution of load. To accon'iplish this, instead of splitting the trunks into uniform divisions determined by the maximum number of simultaneous calls originating atthe primary points which they serve, I divide the trunk multiple. varying the number of appearances at diie'rent primary points, this depending upon their order of use. Moreover, these divisions of the multiple are arranged in sections with respect to the terminals to which the trunks are united in the primary apparatus, the multiple groups of-successive sections being rotated or progressively varied. A concrete case of this graded multiple will now be described, in its applica} tio'n t'oa system in which the same general coalitions ,oflma'chines and their'terminals obtain as have just been set forth. Although no attempt has been made to present This is due. to

an example giving the greatest efliciency. the gain resulting from the en'iployment of my method is clearly shown. a

In the accompanying drawings, Figures 1, 2 and 3, taken together,- furnish a diagrammatic illustration in detail of my improved system of connection; Fig. 4 is a schematic representation of the same; and Fig. 5 1s a schemaof another embodiment of the invention.

Referring toFigs. 1, 2 and 3; switches S are illustrated which may be considered as primary selectors of any convenient type, these switches having the usual mova le arms or members s, commonly arranged in or terminal .9 of which there are Lwentyfive, numbered consecutively from one to twenty-five in the order in which the-arms coo crate with them. -The selected terminal asconnected to ita trunk or set of conductors T leading to the arm 8 of a secondary selector or connector S. Only two of these s'econdary'switchesare illustrated, and with but a portion of their five hundred fixed terminals. To said terminals are joined the substation lines, among which is that of the called subscriber. For present purposes we need only consider the calls intended for a single five-hundred group reached through the section of'the primary switches whichhas been illustrated. As is the case in the ordinary divided multiple, it is necessary to make some such preliminary separation of the primary switches that divisions will be obtained from which the calls into the selected five-hundred group will not exceed the trunk capacity of the section (25) during the busiest two-minute period; As

before, twelve have been taken, over which thecalls are distributed as already tabulated. The letters from a to Z inclusive, also designate these divisions, and within each the apparatus is multipled in the usual manner-by conductors t, this being indicated' only at aand Z, so that an switch may appropriate any unused trun of those multipled to its division. .But now instead of "maintaining-these divisions in four rigid groups fo'f threeeach, with twenty-five trunks multipl'edthrou'ghout the series of twentyfive contacts of 1;, ch sections, the terminals which come firs in the sections and are therefore most used, this belng here shown as'the sets numbered from one to twelve inwill be seen that the trunks available to continue the circuit fromthe later terminals are not multipled unduly, the extent ofthe multipling in each, case hearing a definite relation to the amount which the particular set of terminals is used and therefore tending to give a uniform load upon all trunks. As to the first twelve setsof terminals, the

load'is distributed and any tendency to con-.

gcstion within their groups of divisions is relieved by rotating the multipled groups with respect to one another. for the firstfour sets of terminals beginning with terminal, 1,- divisions, a, Z), a; (Z, 6, f," g, 11., i; 7, is, Z are multipled to separate trunks, for the second section comprising the sets of terminals 5, 6, 7 and 8 the multipled groups consist ofb, 0, (Z; 6, f, g; h, 2', j; 70, Z, a, and for the third four sets of terminals 9, 10, 11 and 12 they comprise divisions p, (Z, e; f, g, h; i, j, 711; Z, a, b, all groups being uniform in the number of divisions but. varying witlLrespectto the particular divisions constituting the groups of different terminal sets. So a call from division (6 may not only find its way over a.

trunk used with b and 0, and in the last thirteen sets of terminals with all the divisions in common, hit also in the earlier] busy groups with tlffe divisions Z0 and Z. As it is improbable that the busy period of these various divisions will coincide, the loadon the trunks is equalized. The service is now handled by sixty-one trunks where one hundred were necessary with the simple divided multiple. )Vhen it is remembered that each trunk must have at its termination a comparatively costly automatic machine, the

gain in economy in dispensing with thirtynine trunks in one hundred will be appreelated.

The grading of the multiple in regard to both the different number of appearances of'the trunks and the rotating of the groups is very clearly brought out in Fig. l of the drawings, in connection with which the previous description of the first three figuues maybe easily read. Here the horizontal,

row of squares a to Z indicate the primary points or divisions. Each of the horizontal straight lines corresponds to a trunk multipled-to the set of terminalsin the primary "switches the number of which is shown in the vertical column of figures at the left, and through the divisions below,

Thus, Whilewhich dots are placed upon the lines. The

figures at the right of each line indicate the numbers .of the trunks and correspond to those of Figs. 1, 2 and 3. Considering any particular trunk, say No. 48, a glance at Fig. .lshows that it is multipled to the twelfth terminal'through divisions z', j, and

connected to the thirteenth terminal in all twelve divisions. A similar scheme for the divided multiple as previously practiced and with which my invention has been here- .in compared, would consist of four-columns of. lines each extending beneath three primary points. That is, four sections of twenty-five trunks each, instead of sixty one trunks with which I am able to handle the same volume of trafiic. By my organization there is attained a trunk-efliciency of ninety three. per cent, .While by the arrangement of previous practice an 'etficiency "/0, while the trunk next in number, 4&9, is

of only fifty-seven percent. is secured. To

demonstrate that the fifty-seven'calls actually can be disposed of over sixty-one trunks during the busy two-minute period, said period will be divided into eight fifteensecond intervals and each call will be considered to originate at the beginning of some one of hese intervals- To still more closely approach: the conditions of practice apreceding two-minute period will be assumed during which forty five calls will occur which may overflow into the busy period and which are distributed through the We therefore have sixteen fifteen-second intervals during which one hundred and two calls must be cared for. These have been allowed to fall by chance as shown in the following 11st, in which each call is des ,ignated by numeral and a letter, the former 1I1(l1(33.t};ng'111 which of the fifteen second intervals it occurs and the latter the division in which it originated. A serial nuniber' in brackets is-also affixed fen; convenience in distinguishing the calls First Busy First Busy First (Busy period. period. period period. period. period. (1) 1- (46) 9-g (20) 4d (65) 12-1 39) 7-j (84) 14-e 2) 1-1:) (4'1) 91! (21) 4-(1 (66) 12-1? 40) 721 (85) 14-h 3) 1-3 (48) 9 (1 (22) 4-k (67) 12h (41) 1-43, (86) 14t (4) 1j (49) 9-0 (23) 4--k (68) 12& (42) 7'-fl., (87) 14-d (5) 1a -(50) 9 -1 (24 4-] 69) 12k (43) 8.b (88) 14-0. (6) 1l (51) 9'g (25) 4 a (70) 13-f (44) 8 ('89) 14-a 7 1-1 52 10-4; (26) 4-1; 71) 13-1 (45) 8-b 15-k' (8) 2-11 (53) 10-f (27) 5-c (72) 13-11 1 ,(91) 15g (9) 2-c (54) 10-f (28) 5h. (73) 13e !(92)15e (10) 2a (55)10,g (29)}3-1 (74) 13-i (93) 15-0 (11) 2-c (56) 115-(1 (30) 5-k (75) !3-h (94) 16'-h (12) 2n. 7) 11'o' (31) 6k (76) 13k (595) 16-4 (13.) 3-6 (5)8)..11-(1 (32) 6-d (77) J3---] ($6) 1 (14) 3f (59) 11-f (33) 6(1 (78) 13-'& (1 7) 16f (15, 3-j (60) 11-9 (34) 6- (79) 13-9. (98) IG-e (16) 3-k (61) 11-11 35) 6j (80) 'l3b (99) 16-;6 (17) 3- (62). 11-1 36) 6--o (81.) 13-g (100) 16-k (18) 3-b (63) 11-e (37) 6-b (82) ll-d (101) 16 l (19) 4i (64) 11-9 (38) 7-j (83) 14-f (102) 16-11.-

Thiese calls are disposed of as shown be-' low,the first column giv'ing'the number of divisions as follows Divisions a b c d e f g h i j k l callsumun fl 6.74 6 1 1 O l 1 6 7 5v Trunks. Calls.

the "trunk used and the second the designa- .The arrangement of n ultipling which has just been described is a simple one, in

number to ,those in the instance from previous and standard; PIELCiLICG'Of dlvlding the multiple already mentioned, it having been chosen for the purpose of more clearly illustrating the'feature of rotation. It does not,

however, exemplify the reduction in the niultipling of the busier sets of terminals by assigning the trunks to the service of a less number 5 of divisions. Such a system more intricate in character but attaining greater economy in trunks is illustrated schematically in Fig. 5 of the drawings,

which generally follows the plan of Fig. 4, the twelve divisions, however, having been reduced to six, in which it may be considered that the apparatus of the previous case is consolidated as indicated by the pairs of reference letters. As the sets of terminals now involved are not .the same throughout all the multipled groups, each terminal dot has its own number placed at the left, there being n0w assumed to be twenty-three of these in each five-hundred section of the primaryswitches. An inspection of this figure will make it plain that the first orbusiest terminal has the exclusive use of a trunk in v Trunks ls. 1 5).1--a. (49) 9-c. 32. 15) 3-. (61) 11h. 2. 1) 1b. 57)11c. 33. 37) 6- .(102) 16-11.. 8. 2) 1b.-(68) 12-11 34. 26) 4--b. Idle; 4. r 10) 2-51. (725)13-a 35. 29) 5l.- Idle. 5. (8 2-d.-- (53).10-'-f 36. (24; 4-1. Idle. 6. (13) 3-e. (136)11 87. 27 5-0. (73) 13--e. 7. (20) 4-d. (65) 12-f 38. (86) 6-0. 92) 15-e. 3- ti?) 2" 23' ttt; 223' 33%?- g. e. 10. (46) 9-g. 41. (59)11-.-f. 11. (28) 5 -11. 81)13g. 42. (66) 12-f 12. (19) 4-i. 67)12l1. 43. 13[ 13. 3) 1-j. -69)12k. 44. 8B 14-f. I 14. (4) 1- 76)13"k. 45. (31) 6k. Idle.

15. (6) 1-1. 52)10-k. 46. 30) 5-k. ('71) 13-1. 16. (7) 1-l. 50; 9*]. 47. 23) 4-k. (100) 16-h. 17. 12) 2-a. (79 13-8.. 48. (22) 4-4;. (90) 15-41. 18. 16) 3-k. 77g13-1. 49. (40).,7-a. (96)16-d 19. (17) 3-k. E88 14-a. 1 50. (4'2) 7-a. (91)15g. W0. (25) 4'a. (89) 14-11 51. (43) 8-b.- 99)16e. 21. 2 9) 2-0. 80) 13-h 52. (4' 8-b. 98) 16-0. 22. 11; 2-c. (74)13c 53. (97) 16-f. 23. (21 4-11. (82) 14-6 54. (41) 7-(1. (93)15c. 24. (1S) 3-K (72)13d 55. (48) 9-d. 25. (60) 11-e 56. 63) 11e. (are (as-s.- ID 28. (51) 9-g. 59. (62)111 29. 3e 7-j (an 16-11 00. (34) 6-1: (8G)1-l--f. 30. (3S) 7j (101)1(t-i 61. i l) 8-4. (95) 16-1'. 31. (35) 6- (851)14-11 of division 0; b and the third set of the others, and so on until 7 8, 9, 10 and 11 cl division 70 l are united to the eleventh terminal 'set of the companion divisions. This requires thirty more trunks. Next the divisions are multipled in all the combinations of three, thus adding twenty trunks. Finally two trunks are each joinedto the twenty-second and twenty-third sets of terminals throughout the divisions. This arrangement of the multiple. is even more efficient than that first described, for it will be found that but fifty-eight trunks connected to twenty-three terminals will'enable the previously assumed set of calls to be cared for. The improved result, however, flows from the same broad principle of providing for a ditte'rentnumber of appearances of "the trunks in the multiple in accordance with the'order in which they are used, and of progressively varying the multiple groups which contain certain divisions in common.

I claim: I

1. The method of connecting telephone conductors between primary points and other points which consists in causing each conductor to appear at one or more ofthe primary. points, the number of such appearances differing with different conductors and arranging said appearances so that conductors are used only in'a definite order with reference to other conductors.

2; The method of 'multipling a series of telephone conductors connecting primary points andsecondary points which consists in causing each conductor to appear at one or more of the primary points, the number of such appearances varying according to the order ofuse of the conductor and arranging said appearances so that conductors are used only in a definite order with reference to other conductors.

3. The method of connecting conductors between primary points and other Joints, consisting .in rendering said con uctors available at groups of primary points arranged in permutations and arranging said conductors to be available at their primary points in a definite order with reference to the availability of other conductors.

4. The method of multipling telephone trunks connecting a series of transmitting points with other points of the system which consists in causing each'trunk to appear at one or more transmitting points, the number of such appearances difi'ering with different trunks, and in rendering certain of the trunks available at a plurality of progressively, varying groups of transmitting points, substantially as set forth.

A telephone system comprising a series of switching apparatus, other apparatus to which said switching apparatus are to be connected, and conductors joined to said other apparatus and with difi'erent conductors multipled through different numbers of switching apparatus, the total number of these multiples orappearances ateach switch being the same, and each conductor multipled to a switchin apparatus being arranged to be there used 111 a definite order with reference to other conductors multipled to said apparatus;

6. A telephone system comprising switch.- ing apparatus arranged in a series of divisions, secondary apparatus to which said switching apparatus are to be connected, and. intermediate conductors extending to the secondary apparatus, different conductors being multipled through different groups of divisions but with certain of the divisions common to a plurality of groups.

7. A telephone system comprising divisions of selecting apparatus provided with contacts, other apparatus to which said selecting apparatus are to be connected, and conductors extending to the last-named apparatus and being multipled to sets of contacts through groups of divisions of the selecting apparatus,.said groups being arranged in rotation with respect to successive contacts.

8. A telephone system comprising divisions of selecting apparatus, other apparatus, and conductors extending to the lastnamed apparatus, certain of said conductors being multipled through equal groups of divisions of the selecting apparatus and with the groups arranged in rotation and having divisions common to certain groups, and otherof the conductorsbeing multipled through groups including a different number of divisions, substantially as described.

9. The combination with a series of switches each having a series of terminals and a movable member for successive cooperation therewith, of trunks for extend ing the circuit from the switches, with different trunks multipled toa different number of terminals in the various switches, the total number of terminals at each switch to which the trunks are thus multipled being the same for all of the switches.

10. The combination with a series of switches each having a series of terminals and a movable member for successive cooperation therewith, of trunks for'extending the circuit from the switches and being multipled to the terminals, the multipling of the*terminals with which the movable member first cooperates being less frequent than to those later in the series.

11. In a telephone exchange system, the combination with a series of electromechanical switches each having a series of terminals and a movable contact member for cooperation therewith, of trunks for extendterminals from the first-named groups.

12. In a telephone exchange system, the combination with switching mechanisms each having a movable contact member and a series oftermiiials with which the movable member coiiperates in a definite order, of trunks connected to groups of terminals formed among sets of terminals which occupy corresponding positions in the series, the groups of different terminal sets being differently arranged with respect to the switches the terminals of which are included therein.

13. In a telephone exchange system, the combination with switching mechanisms each having a movable contact member and a series of terminals with which the movable member cooperates in a definite order, of trunksconnected to groups of terminals formed among sets of terminals which occupy corresponding p0 iti0118 in the series, a group of one terminal set including the terminals of switches belonging to a plurality of groups in another set.

14. In a telephone exchange system, the combination with switching mechanisms each having a movable contact member and a series of terminals with wh ch the movable member cotiperates in a definite order, of trunks connected to groups of terminals formed among sets of terminals which occupy corresponding positions in the series,

said groups being also arranged in sections consisting of a plurality of terminal sets, the corres )ond. 1g groups in all the terminal sets 0t one section including the terminals of the same switches and the groupsiof another section being differently constituted.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses, this twenty-third day of July 1907.

ERNEST A. GRAY. Witnesses:

TnoMAs D. LOCKWOOD, WILLIAM PEARSON.

{topics of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. C. I 

